1. Field of the Invention
The present invention is broadly concerned with pill dispensing devices as well as with storage and dispensing cassettes useful in automated dispensing equipment and especially for use in pill dispensing devices.
2. Description of the Background
U.S. Pat. No. 4,018,358 covers the Drug-O-Matic (DOM) cassette and counting machine available from McKesson Automation Systems Inc. of Pineville, La. The original DOM cassette relied upon a pill separator positioned to separate the pills from the conveying wheel to release the pills into the discharge chute. U.S. Pat. No. 4,697,721 covers improvements made to the DOM cassette including the addition of two chambers, one for storage and one for dispensing, and an adjustment mechanism to partially cover the holes in the conveying wheel.
U.S. Pat. No. 6,053,302 issued to Leu et.al. describes a cassette based counter for pharmaceutical products using vacuum technology and pick up tubes. The vacuum is removed from the product to allow inertia to release the pill into a discharge tube. The '302 patent requires precise timing of the vacuum shut off and must be adjusted for each pill type. Adjustment of the vacuum shut off for each type of pill requires the operator to spend a considerable amount of time before dispensing a new pill type for a patient prescription. Another limitation of the '302 patent is that it relies on inertia to ‘throw’ the pill from the pickup tube into the discharge chute when the vacuum is released; the design does not appear to allow a pill released from the pickup tube to fall under gravity into the discharge tube. Another limitation is the ends of the pick up tubes are modified to accommodate different pill shapes and may include the application of an adhesive to promote the adherence of pills to the pick up tube. The count speed of the '302 patent is less than half of the previous vacuum pill counting devices when operating at the same revolutions per minute. Increasing the motor speed is unlikely to improve the performance due to the reduced efficiency of the pickup tubes at higher speeds and the likelihood of the pickup tubes damaging or breaking the pills in the hopper.
U.S. Pat. No. 5,061,145 by Genis et.al. describes an article dispenser using vacuum and pick up tubes rotating in a drum. The vacuum source in the pick up tube is removed and replaced by an air pressure source to dispense the article.
There is accordingly a need for an improved pill storage and dispensing cassette, which improves the vacuum airflow efficiency, reduces noise level, improves pill agitation between the storage and dispensing compartments to insure free flow of pills for dispensing, sets the calibration to a predetermined setting prior to dispensing, allows pre-counting and dispensing into a discharge chute and primes the conveying wheel before dispensing.